398 Factors Associated With Inconclusive Ultrasound in Pediatric Appendicitis

Abstract

Acute appendicitis is the most common surgical emergency among pediatric patients in the emergency department (ED). Due to the increased risk of radiation associated with computed tomography, the American College of Emergency Physicians recommends considering ultrasound as the initial radiologic modality in diagnosing pediatric appendicitis. Ultrasound for appendicitis may often be inconclusive and necessitates further imaging, thus leading to delay in diagnosis and disposition of the patient. The objective of this study was to determine the factors that may predict inconclusive ultrasound. Retrospective analysis was done on all cases of appendicitis at a large tertiary care pediatric hospital that had an ultrasound performed in the ED as part of their initial work up from January 2015 to December 2020. Patients were included if they had an age less than or equal to 18 years and had appendicitis confirmed on surgical pathology. Patients were excluded if an alternate diagnosis was found on pathology or if their appendix was not removed during the same hospitalization. A multivariate analysis was used to assess the rates of inconclusive ultrasound and determine which demographic and clinical factors were related to inconclusive ultrasound. All tests were two-sided and performed using SAS EG 7.13 (Cary, NC). P values of less than 0.05 were considered statistically significant. Ultrasound was inconclusive in 1,013 patients of the 2,925 patients who met all criteria (34.6%). Independent risk factors for inconclusive ultrasound were higher weight-for-age percentile (0.8% increased risk per percentile, p<0.0001), female sex (27% increased risk than male sex, p=0.01), and lower white blood cell count (2% increased risk per 1, 000/μL, p=0.02). Weight-for-age percentiles corresponding to normal weight-for-age (0-75th percentile), overweight (76th-89th percentile), and obese (90th-100th percentile) correlated with inconclusive ultrasound findings in 29.5%, 36.1%, and 43.3% of the patients, respectively. Older age was borderline significant and led to a 2% increased risk of inconclusive ultrasound per year (p=0.0595). Factors not correlating with ultrasound findings were CRP, temperature, presence of rupture, and race or ethnicity. Inconclusive ultrasound findings in pediatric patients with appendicitis are predicted by higher weight-for-age percentiles, lower white blood cell counts, female sex and, to a lesser degree, increased age. Based on this study, ultrasound is appropriate as the initial imaging modality in pediatric patients with appendicitis, including those in the highest percentiles of weight-for-age.